Bentonite-containing drilling fluid and preparation method thereof

Abstract

The invention relates to the technical field of drilling fluids, and discloses a bentonite-containing drilling fluid and a preparation method thereof.The bentonite-containing drilling fluid is obtained by adding modified polyurethane, bentonite, a calcium chloride solution, a Tween 20 emulsifier and white oil into a stirrer and stirring. A quaternary ammonium salt group in the modified polyurethane interacts with clay particles, so that hydration dispersion of the clay can be effectively inhibited, the stability and rheological property of the drilling fluid can be maintained, and the phenomenon of filtration loss is reduced; wherein the polyurethane absorbs water and expands underground to form a high-strength elastic body which enters cracks in a well wall so as to achieve a plugging effect, and the nitrile rubber has an elastic deformation characteristic and can also enter the cracks in the well wall so as to achieve the plugging effect; and the adamantyl group contained in the drilling fluid improves the high temperature resistance of the drilling fluid.

Description

Technical Field

[0001] The invention relates to the technical field of drilling fluid, in particular to a drilling fluid containing bentonite and a preparation method thereof. Background Art

[0002] With the development of high-temperature deep wells and complex well oil and gas resources, new challenges have been raised for drilling fluids in drilling operations. Especially for unstable shale formations, the requirements for drilling fluid filtration and inhibition performance are getting higher and higher. Bentonite can form a dense filter cake in the drilling fluid, effectively blocking the pores of the well wall rock, thereby reducing the penetration of the drilling fluid into the formation and reducing the filtration loss. Therefore, developing a drilling fluid with bentonite is the key to solving the problem.

[0003] For example, CN101935519A discloses a drilling fluid and its preparation method. The drilling fluid provided by the invention is suitable for leaking formations and has a significant plugging effect. It also has the function of leak prevention and has a significant inhibitory effect on easily dispersed and easily collapsed formations; however, its filtration loss reduction effect needs to be improved. Summary of the invention

[0004] 1. Technical issues to be resolved In view of the deficiencies in the prior art, the present invention provides a drilling fluid containing bentonite and a preparation method thereof, which has good plugging performance, high temperature resistance and reduced filtration loss.

[0005] (II) Technical solution To achieve the above object, the present invention provides the following technical solution: a drilling fluid containing bentonite, comprising the following components by weight: 3-6 parts by weight of modified polyurethane, 2-5 parts by weight of bentonite, 0.5-1.2 parts by weight of calcium chloride solution, 0.9-1.3 parts by weight of Tween 20 emulsifier, and 30-45 parts by weight of white oil.

[0006] Preferably, the preparation method of the quaternized chitosan modified polyurethane is: Step 1: Add magnolol and 3-mercaptopropionic acid to a dichloromethane solvent, stir evenly, add benzoin dimethyl ether catalyst, irradiate with ultraviolet light at 25-40° C. in a dark environment for 1-2 h, centrifuge, wash and dry to obtain intermediate 1; Step 2: Add 6-10 parts by weight of intermediate 1 and 0.2-0.3 parts by weight of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide salt to an ethanol solvent, stir at room temperature for 20-30 minutes, continue to add 0.1-0.3 parts by weight of N-hydroxysuccinimide, react in an ice bath for 40-60 minutes to obtain solution A, add 5-8 parts by weight of chitosan hydrochloride to a mixed solution of ethanol and water in a volume ratio of 2:1 to obtain solution B; add solution A to solution B, react at room temperature for 12-24 hours, control the pH to 4.2-5.8, centrifuge after completion, wash with ethanol, and obtain alkenyl chitosan; Step 3: 0.8-1.3 parts by weight of sodium dodecyl sulfate emulsifier, 5-10 parts by weight of alkenyl chitosan, 4-7 parts by weight of 1,3-adamantanediol diacrylate, and 8-12 parts by weight of allyl trimethylammonium chloride are introduced into a nitrogen atmosphere for protection, and then 0.2-0.4 parts by weight of azobisisobutyronitrile initiator are added, reacted at 85-108° C., washed with deionized water and ethanol in turn, and dried to obtain a chitosan chain extender; Step 4: Add polyethylene glycol and dimethylolbutyric acid to the reactor, stir evenly, continue to add toluene diisocyanate, react at 65-80°C for 4-5h, then continue to add chitosan chain extender, react at 45-60°C for 1-2h, and obtain quaternized chitosan modified polyurethane after completion; Step 5: Mix nitrile rubber, quaternary ammonium chitosan modified polyurethane, polyacrylamide, and plasticizer dioctyl phthalate, and press at high temperature using a flat vulcanizer. Heat and react at 120° C., 130° C., and 150° C. for 1-1.5 hours, respectively, and obtain modified polyurethane after cooling.

[0007] Preferably, in the step 1, the mass ratio of magnolol, 3-mercaptopropionic acid and benzoin dimethyl ether catalyst is 1:2.1-2.4:0.02-0.03.

[0008] Preferably, in step 2, the volume ratio of solution A to solution B is 1:0.8-1.1.

[0009] Preferably, the reaction time in step three is 1-3h.

[0010] Preferably, in step 4, the mass ratio of polyethylene glycol, dimethylolbutyric acid, toluene diisocyanate, and chitosan chain extender is 3.5-4:1:2.5-3.2:0.4-0.6.

[0011] Preferably, in the step five, the mass ratio of nitrile rubber, quaternized chitosan modified polyurethane, polyacrylamide, and plasticizer dioctyl phthalate is 1.8-2:1:1.2-1.3:0.1-0.2.

[0012] Preferably, the preparation method of the bentonite-containing drilling fluid is: adding modified polyurethane, bentonite, calcium chloride solution, Tween 20 emulsifier, and white oil into a stirrer, stirring for 10-12 minutes, and obtaining the bentonite-containing drilling fluid.

[0013] 3. Beneficial technical effects The invention prepares the drilling fluid containing bentonite by adding modified polyurethane, bentonite, calcium chloride solution, parts of Tween 20 emulsifier and white oil into a stirrer and stirring.

[0014] The quaternary ammonium salt groups in the modified polyurethane can effectively inhibit the hydration and dispersion of clay through interaction with clay particles, which helps to maintain the stability and rheology of the drilling fluid, thereby reducing the occurrence of filtration loss; the polyurethane therein absorbs water and expands underground to form a high-strength elastic body, which enters the cracks in the well wall to achieve a plugging effect; the nitrile rubber therein has elastic deformation characteristics and can also enter the cracks in the well wall to achieve a plugging effect; the adamantane group contained therein improves the high temperature resistance of the drilling fluid; the chitosan group and bentonite therein can also reduce the effect of filtration loss. DETAILED DESCRIPTION Example 1

[0015] (1) Add magnolol and 3-mercaptopropionic acid to a dichloromethane solvent, stir evenly, and then add benzoin dimethyl ether catalyst, wherein the mass ratio of magnolol, 3-mercaptopropionic acid, and benzoin dimethyl ether catalyst is 1:2.1:0.02, and irradiate with ultraviolet light at 25° C. in a dark environment for 1-2 h. After the irradiation, centrifuge, wash, and dry to obtain intermediate 1; (2) 6 parts by weight of intermediate 1 and 0.2 parts by weight of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide salt were added to an ethanol solvent, stirred at room temperature for 20 minutes, and then 0.1 parts by weight of N-hydroxysuccinimide were added. The mixture was reacted in an ice bath for 40 minutes to obtain a solution A. 5 parts by weight of chitosan hydrochloride were added to a mixed solution of ethanol and water in a volume ratio of 2:1 to obtain a solution B. Solution A was added to solution B, wherein the volume ratio of solution A to solution B was 1:0.8, and the mixture was reacted at room temperature for 12 hours. The pH was controlled to be 4.2. After the reaction, the mixture was centrifuged and washed with ethanol to obtain alkenyl chitosan. (3) 0.8 parts by weight of sodium dodecyl sulfate emulsifier, 5 parts by weight of alkenyl chitosan, 4 parts by weight of 1,3-adamantanediol diacrylate, and 8 parts by weight of allyl trimethylammonium chloride were introduced into a nitrogen atmosphere, and then 0.2 parts by weight of azobisisobutyronitrile initiator was added, and the mixture was reacted at 85° C. for 1 hour, and then washed with deionized water and ethanol in turn, and dried to obtain a chitosan chain extender; (4) Add polyethylene glycol and dimethylolbutyric acid to the reactor, stir evenly, continue to add toluene diisocyanate, react at 65°C for 4 hours, and then continue to add chitosan chain extender, wherein the mass ratio of polyethylene glycol, dimethylolbutyric acid, toluene diisocyanate, and chitosan chain extender is 3.5:1:2.5:0.4, react at 45°C for 1 hour, and obtain quaternary ammonium chitosan modified polyurethane; (5) mixing nitrile rubber, quaternary ammonium chitosan modified polyurethane, polyacrylamide, and plasticizer dioctyl phthalate, wherein the mass ratio of nitrile rubber, quaternary ammonium chitosan modified polyurethane, polyacrylamide, and plasticizer dioctyl phthalate is 1.8:1:1.2:0.1, and pressing at high temperature using a flat vulcanizer, heating at 120°C, 130°C, and 150°C for 1 hour, respectively, and cooling to obtain a modified polyurethane; (6) Add 3 parts by weight of modified polyurethane, 2 parts by weight of bentonite, 0.5 parts by weight of calcium chloride solution, 0.9 parts by weight of Tween 20 emulsifier, and 30 parts by weight of white oil into a stirrer and stir for 10 minutes to obtain a drilling fluid containing bentonite. Example 2

[0016] (1) Add magnolol and 3-mercaptopropionic acid to a dichloromethane solvent, stir evenly, and then add benzoin dimethyl ether catalyst, wherein the mass ratio of magnolol, 3-mercaptopropionic acid, and benzoin dimethyl ether catalyst is 1:2.4:0.03, and irradiate with ultraviolet light at 40° C. in a dark environment for 2 h. After the irradiation, centrifuge, wash, and dry to obtain intermediate 1; (2) 10 parts by weight of intermediate 1 and 0.3 parts by weight of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide salt were added to an ethanol solvent, stirred at room temperature for 30 minutes, and 0.3 parts by weight of N-hydroxysuccinimide was added. The mixture was reacted in an ice bath for 60 minutes to obtain a solution A. 8 parts by weight of chitosan hydrochloride was added to a mixed solution of ethanol and water in a volume ratio of 2:1 to obtain a solution B. Solution A was added to solution B, wherein the volume ratio of solution A to solution B was 1:1.1, and the mixture was reacted at room temperature for 24 hours. The pH was controlled to be 5.8. After the reaction, the mixture was centrifuged and washed with ethanol to obtain alkenyl chitosan. (3) 1.3 parts by weight of sodium dodecyl sulfate emulsifier, 10 parts by weight of alkenyl chitosan, 7 parts by weight of 1,3-adamantanediol diacrylate, and 12 parts by weight of allyl trimethylammonium chloride were introduced into a nitrogen atmosphere, and then 0.4 parts by weight of azobisisobutyronitrile initiator was added, and the mixture was reacted at 108° C. for 3 h, and then washed with deionized water and ethanol in turn, and dried to obtain a chitosan chain extender; (4) Add polyethylene glycol and dimethylolbutyric acid to the reactor, stir evenly, continue to add toluene diisocyanate, react at 80°C for 5 hours, and then continue to add chitosan chain extender, wherein the mass ratio of polyethylene glycol, dimethylolbutyric acid, toluene diisocyanate, and chitosan chain extender is 4:1:3.2:0.6, react at 60°C for 2 hours, and obtain quaternized chitosan modified polyurethane after the reaction; (5) mixing nitrile rubber, quaternary ammonium chitosan modified polyurethane, polyacrylamide, and plasticizer dioctyl phthalate, wherein the mass ratio of nitrile rubber, quaternary ammonium chitosan modified polyurethane, polyacrylamide, and plasticizer dioctyl phthalate is 2:1:1.3:0.2, and pressing at high temperature using a flat vulcanizer, heating at 120°C, 130°C, and 150°C for 1.5 hours, respectively, and cooling to obtain modified polyurethane; (6) Add 6 parts by weight of modified polyurethane, 5 parts by weight of bentonite, 1.2 parts by weight of calcium chloride solution, 1.3 parts by weight of Tween 20 emulsifier, and 45 parts by weight of white oil into a stirrer and stir for 12 minutes to obtain a drilling fluid containing bentonite. Example 3

[0017] (1) Add magnolol and 3-mercaptopropionic acid to a dichloromethane solvent, stir evenly, and then add benzoin dimethyl ether catalyst, wherein the mass ratio of magnolol, 3-mercaptopropionic acid, and benzoin dimethyl ether catalyst is 1:2.3:0.025, and irradiate with ultraviolet light at 350° C. in a dark environment for 1.5 h. After the irradiation, centrifuge, wash, and dry to obtain intermediate 1; (2) 80 parts by weight of intermediate 1 and 0.2 parts by weight of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide salt were added to an ethanol solvent, stirred at room temperature for 25 minutes, and 0.2 parts by weight of N-hydroxysuccinimide was added. The mixture was reacted in an ice bath for 50 minutes to obtain a solution A. 6 parts by weight of chitosan hydrochloride was added to a mixed solution of ethanol and water in a volume ratio of 2:1 to obtain a solution B. Solution A was added to solution B, wherein the volume ratio of solution A to solution B was 1:0.9, and the mixture was reacted at room temperature for 16 hours. The pH was controlled to be 5.3. After the reaction, the mixture was centrifuged and washed with ethanol to obtain alkenyl chitosan. (3) 1.2 parts by weight of sodium dodecyl sulfate emulsifier, 9 parts by weight of alkenyl chitosan, 6 parts by weight of 1,3-adamantanediol diacrylate, and 10 parts by weight of allyl trimethylammonium chloride were introduced into a nitrogen atmosphere, and then 0.3 parts by weight of azobisisobutyronitrile initiator was added, and the mixture was reacted at 95° C. for 2 h, and then washed with deionized water and ethanol in turn, and dried to obtain a chitosan chain extender; (4) Add polyethylene glycol and dimethylolbutyric acid to the reactor, stir evenly, continue to add toluene diisocyanate, react at 75°C for 4 hours, and then continue to add chitosan chain extender, wherein the mass ratio of polyethylene glycol, dimethylolbutyric acid, toluene diisocyanate, and chitosan chain extender is 3.6:1:2.8:0.5, react at 55°C for 1 hour, and obtain quaternary ammonium chitosan modified polyurethane; (5) mixing nitrile rubber, quaternary ammonium chitosan modified polyurethane, polyacrylamide, and plasticizer dioctyl phthalate, wherein the mass ratio of nitrile rubber, quaternary ammonium chitosan modified polyurethane, polyacrylamide, and plasticizer dioctyl phthalate is 1.9:1:1.2:0.15, and pressing at high temperature using a flat vulcanizer, heating at 120°C, 130°C, and 150°C for 1.2 hours, respectively, and cooling to obtain modified polyurethane; (6) Add 5 parts by weight of modified polyurethane, 4 parts by weight of bentonite, 0.8 parts by weight of calcium chloride solution, 1.2 parts by weight of Tween 20 emulsifier, and 35 parts by weight of white oil into a stirrer and stir for 11 minutes to obtain a drilling fluid containing bentonite. Example 4

[0018] (1) Add magnolol and 3-mercaptopropionic acid to a dichloromethane solvent, stir evenly, and then add benzoin dimethyl ether catalyst, wherein the mass ratio of magnolol, 3-mercaptopropionic acid, and benzoin dimethyl ether catalyst is 1:2.1:0.02, and irradiate with ultraviolet light at 25° C. in a dark environment for 1-2 h. After the irradiation, centrifuge, wash, and dry to obtain intermediate 1; (2) 6 parts by weight of intermediate 1 and 0.2 parts by weight of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide salt were added to an ethanol solvent, stirred at room temperature for 20 minutes, and then 0.1 parts by weight of N-hydroxysuccinimide were added. The mixture was reacted in an ice bath for 40 minutes to obtain a solution A. 5 parts by weight of chitosan hydrochloride were added to a mixed solution of ethanol and water in a volume ratio of 2:1 to obtain a solution B. Solution A was added to solution B, wherein the volume ratio of solution A to solution B was 1:0.8, and the mixture was reacted at room temperature for 12 hours. The pH was controlled to be 4.2. After the reaction, the mixture was centrifuged and washed with ethanol to obtain alkenyl chitosan. (3) 1.3 parts by weight of sodium dodecyl sulfate emulsifier, 10 parts by weight of alkenyl chitosan, 7 parts by weight of 1,3-adamantanediol diacrylate, and 12 parts by weight of allyl trimethylammonium chloride were introduced into a nitrogen atmosphere, and then 0.4 parts by weight of azobisisobutyronitrile initiator was added, and the mixture was reacted at 108° C. for 3 h, and then washed with deionized water and ethanol in turn, and dried to obtain a chitosan chain extender; (4) Add polyethylene glycol and dimethylolbutyric acid to the reactor, stir evenly, continue to add toluene diisocyanate, react at 80°C for 5 hours, and then continue to add chitosan chain extender, wherein the mass ratio of polyethylene glycol, dimethylolbutyric acid, toluene diisocyanate, and chitosan chain extender is 4:1:3.2:0.6, react at 60°C for 2 hours, and obtain quaternized chitosan modified polyurethane after the reaction; (5) mixing nitrile rubber, quaternary ammonium chitosan modified polyurethane, polyacrylamide, and plasticizer dioctyl phthalate, wherein the mass ratio of nitrile rubber, quaternary ammonium chitosan modified polyurethane, polyacrylamide, and plasticizer dioctyl phthalate is 1.9:1:1.2:0.15, and pressing at high temperature using a flat vulcanizer, heating at 120°C, 130°C, and 150°C for 1.2 hours, respectively, and cooling to obtain modified polyurethane; (6) Add 5 parts by weight of modified polyurethane, 4 parts by weight of bentonite, 0.8 parts by weight of calcium chloride solution, 1.2 parts by weight of Tween 20 emulsifier, and 35 parts by weight of white oil into a stirrer and stir for 11 minutes to obtain a drilling fluid containing bentonite.

[0019] Comparative Example 1 Compared with Example 4, this comparative example differs in that polyurethane is used instead of modified polyurethane.

[0020] The drilling fluids prepared in the above examples and comparative examples were hot rolled at 210°C for 15 hours, and their rheological properties (including apparent viscosity AV, plastic viscosity PV and dynamic shear force YP) and demulsification voltage Es before and after rolling were measured. The hot rolled drilling fluids were added to a high temperature and high pressure permeability plugging instrument equipped with a core sand tray, sealed, and pressurized with liquid oil to record the sand tray leakage (FL) at 210°C and 1000 psi for 30 minutes. HTHP The sand disc model is 170-53-3, the average pore size is 20 μm, and the test results are shown in Table 1.

[0021] Table 1: The drilling fluid was hot rolled at 210℃ for 16h to test the rheological properties and sand plate loss.

[0022]

[0023] As can be seen from Table 1, in Examples 1-4 and Comparative Example 1, the apparent viscosity AV, plastic viscosity PV, dynamic shear force YP and demulsification voltage Es before and after hot rolling do not change much, indicating that the drilling fluid of the present invention has good stability and high temperature resistance. From the rate loss, it can be concluded that the present invention has good plugging performance, rheology, and thermal stability, and improves the high temperature plugging performance of the drilling fluid.

[0024] The preferred embodiments of the present invention disclosed above are only used to help illustrate the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to the specific implementation methods described. Obviously, many modifications and changes can be made according to the content of this specification. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can understand and use the present invention well. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. A drilling fluid containing bentonite, characterized in that: The invention comprises the following components by weight: 3-6 parts by weight of modified polyurethane, 2-5 parts by weight of bentonite, 0.5-1.2 parts by weight of calcium chloride solution, 0.9-1.3 parts by weight of Tween 20 emulsifier and 30-45 parts by weight of white oil.

2. The bentonite-containing drilling fluid according to claim 1, characterized in that: The preparation method of the quaternized chitosan modified polyurethane is as follows: Step 1: Add magnolol and 3-mercaptopropionic acid to a dichloromethane solvent, stir evenly, add benzoin dimethyl ether catalyst, irradiate with ultraviolet light at 25-40° C. in a dark environment for 1-2 h, centrifuge, wash and dry to obtain intermediate 1; Step 2: Add 6-10 parts by weight of intermediate 1 and 0.2-0.3 parts by weight of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide salt to an ethanol solvent, stir at room temperature for 20-30 minutes, continue to add 0.1-0.3 parts by weight of N-hydroxysuccinimide, react in an ice bath for 40-60 minutes to obtain solution A, add 5-8 parts by weight of chitosan hydrochloride to a mixed solution of ethanol and water in a volume ratio of 2:1 to obtain solution B; add solution A to solution B, react at room temperature for 12-24 hours, control the pH to 4.2-5.8, centrifuge after completion, wash with ethanol, and obtain alkenyl chitosan; Step 3: 0.8-1.3 parts by weight of sodium dodecyl sulfate emulsifier, 5-10 parts by weight of alkenyl chitosan, 4-7 parts by weight of 1,3-adamantanediol diacrylate, and 8-12 parts by weight of allyl trimethylammonium chloride are introduced into a nitrogen atmosphere for protection, and then 0.2-0.4 parts by weight of azobisisobutyronitrile initiator are added, reacted at 85-108° C., washed with deionized water and ethanol in turn, and dried to obtain a chitosan chain extender; Step 4: Add polyethylene glycol and dimethylolbutyric acid to the reactor, stir evenly, continue to add toluene diisocyanate, react at 65-80°C for 4-5h, then continue to add chitosan chain extender, react at 45-60°C for 1-2h, and obtain quaternized chitosan modified polyurethane after completion; Step 5: Mix nitrile rubber, quaternary ammonium chitosan modified polyurethane, polyacrylamide, and plasticizer dioctyl phthalate, and press at high temperature using a flat vulcanizer. Heat and react at 120° C., 130° C., and 150° C. for 1-1.5 hours, respectively, and obtain modified polyurethane after cooling.

3. The bentonite-containing drilling fluid according to claim 2, characterized in that: In the step 1, the mass ratio of magnolol, 3-mercaptopropionic acid and benzoin dimethyl ether catalyst is 1:2.1-2.4:0.02-0.

03.

4. The bentonite-containing drilling fluid according to claim 2, characterized in that: In the step 2, the volume ratio of solution A to solution B is 1:0.8-1.

1.

5. The bentonite-containing drilling fluid according to claim 2, characterized in that: The reaction time in step 3 is 1-3h.

6. The bentonite-containing drilling fluid according to claim 2, characterized in that: In the step 4, the mass ratio of polyethylene glycol, dimethylolbutyric acid, toluene diisocyanate and chitosan chain extender is 3.5-4:1:2.5-3.2:0.4-0.

6.

7. The bentonite-containing drilling fluid according to claim 2, characterized in that: In the step 5, the mass ratio of the nitrile rubber, the quaternized chitosan modified polyurethane, the polyacrylamide, and the plasticizer dioctyl phthalate is 1.8-2:1:1.2-1.3:0.1-0.

2.

8. A method for preparing a drilling fluid containing bentonite according to any one of claims 1 to 7, characterized in that: The preparation method of the drilling fluid containing bentonite is as follows: adding modified polyurethane, bentonite, calcium chloride solution, Tween 20 emulsifier and white oil into a stirrer, stirring for 10-12 minutes, and obtaining the drilling fluid containing bentonite.

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